Snubber for elevators



'J. mJNLQP 1,873,828

SNUBBER FOR ELEVATORS Filed June 16, 1950 2 sheets-$heec l INVENTOR James Dunlap ATTORNY- Aug. 23, W32 .1: DUNLQP SNUBBER' FOR ELEVATORS 2 Sheets-Sheet 2 June 16, 1930 Filed INVENTOR Jam es flan/0p A'l TORNEY JAMES nunnor,

cending' at a high rat Patented Aug. 23, 1932 UNITED srAJT-Es PATENT OFFICE."

" SNUIBIBER non ELEVATORS I Application filed. June 16,

My invention relates to safety devices for elevators and more specifically to devices for preventing the violent falling back of either the cars or the counterweights when the descent of the other body has been suddenly retarded. Y r V M When an elevator car is moving'at' a sun cientlyhigh rate otspeed .to trip the carsafety means/and-the safety means-is set, the counterweight,,which has been ascend ing, does not stop. as suddenly as the .car, and, by. reason of its. inertia, continuesto ascend until the cables become slack. "The counterweightwill then drop back, pulling the cables taut, and frequently eitherbreakw ing the cables or pulling them aw-ay'from the car or the counterweight. This will occur whenever the car is decelerated at a' rate greater thangravity, whether bystriking the buffer or in any other manner.

If, While traveling :in the opposite direction, the descending counterweight is caught andstopped suddenly the car, which is ase of-speed, will continue movingupward for a short interval of time "after the. counterweight has been retarded. This will cause a slaclr'condition in the cable supporting the car, and, when the car' stops by'gravity and starts descending, it will draw the cables: taut with' asnap, *whereby' they are apt to be broken or'pulled loose from thecarp'w Such conditions are especially apt to occur q in high-speed elevator systems becauseof the high rate of speed at whichthe carer-the counterweight is ascending when the other body is stopped. g i It is, accordingly, an object of my inven tion to provide means for preventing the falling back of either the car or. the counterweight when the downward motion' of the other body has been suddenly retarded? It is also an object of my invention to provide means for retarding the downward mo tion of an elevator body when a slack; condition occurs in-itshoisting' cable. It is more specifically an object of my invention to provide aspring-pressed snubbing device which shall go into action, with slackening of the cables, to provide a braking force 1936. semi no. 461,329.

or R Bins-n, IILINQIS,..ASSIGNQBi-TO.WESTINGHOUSE nrinc'rn'rc ELEVATOR COMPANY, A CORPORATION or rumors forretarding the. reverse movement of the car or the counterweight. v

In accordance with my invention,brake shoes are provided on the car and on the counterweight, and an associated springpressed actuator is provided which tends to engage th'e'brake shoes to force themrint'o engagement with the guide rails. The hoisting cables are attached to a bar which normally engages the spring-pressed actuators to retain them in an inefiective position. If the cables become slack, the retaining bar will .niove away and release the springpressed actuators, which will then apply the brake. My invention, both as to its organization and its'method of operation, together with additional objects and advantages thereof, will best be understood from the following description of a specific embodiment, when read in conjunction with the accompanying drawings, in which: i v

Figure 1 is a view, in side elevation, of an elevator body, which may be either a car or a counterweight, equipped with an automatic.

rail-gripping device in accordance withjmy invention; .Fig. 2 is a detail view, in side elevation, showing one guide rail, a pair of rail-gripping jaws, a cooperating spring-pressed actuator member, and a portion of the retaining barin cooperative relation thereto;

Fig. 3 is an enlarged top'plan view, partly in section along line III-III of Fig. 1 Fig. 4. is a view, showing a modified form of the invention, having the rail-gripping jaws and cooperating elements disposedin the upper cross-head of the car or the counterweight, and I or I a Fig. 5 is an enlarged sectional view of the cross-head, taken on .line V--V of Fig. 4 showing the yoke member, the rail gripping jaws and the actuating member.

Fig. 6 is Referring to the drawings I 'have shown an enlarged cross sectional view p of the cross-head, taken on line VI-VI 0t in Fig. 1 an elevator body B which may be either an elevator car or a counterweight. The elevator body B operates between guide rails 1 and 2 and is supported by hoist cables Ca which may pass over a hoist sheave controlled in any well known manner. Attached to each end of the hoist cables is an elevator body B, one of which is the car and the other the counterweight, in the usual manner.

Mounted at each side of the elevator body is a pair of rail-gripping aws-or brake shoes 4, which may be pivotally mountedas shown in Figs. 1 and 3. Slidably mounted ad acent to each pair of brake shoes is an actuator 5, which carries a wedge 7 at its outer end and rollers 9 on its innermost end. The brackets 6 slidably receive the actuators and support them in cooperative relation to the various adjacent elements. A compression spring 8 is mounted concentrically on each actuator, where it continuously exerts a thrust between the rigid bracket 6 and the wedge-head 7 which tends to move the wedges into engagement with the innermost extremities of the rail-gripping aws. a

The wedges 7 of the actuators are of such shape that, when they are interposed between the inner extremities of the rail-gripping jaws by thesprings 8, they will force them apart, thereby urging the outer extremltles toward each other to grip the guide rails and retard the downward motion of the body B. The springs 8 are normally retained in compressed condition by a yoke-shaped retaining bar 12, the extremities of which engage the rollers 9 and hold the actuators toward thelr innermost positions.

The extremities of the yoke member 12, which engage the rollers 9, constitute cam like surfaces, having diverging portions. This is most clearly shown in Fig. 2. The extremities of the yoke 12 are slotted to receive the ends of the actuators 5 which carry laterally disposed rollers 9. The rollers 9 are urged into cooperative relation to the yoke member by the actuator springs '8, in the manner shown in Fig. 5. Additional guiders'may be provided for the actuator, if desired.

The hoisting cables Ca pass through the cross-head 15 of the'elevator body and are attached to the yoke member 12 in any suitable manner. The weight'of the body is then supported by the upward thrust of the yoke member 12 upon the lower side of the crosshead 15.

Suitable spring means 3 are provided to bias the yoke member 12 away from the crosshead 15. As shown in Figs. 1 and 2, the biasing means consists of compression springs 3 disposed concentrically on the cables and bearing upon .the upper surface of the yoke 12 and the lower surface of the cross-head. In the event that the cables become slackened, or the tension thereof becomes less than a certain predetermined amount, depending upon the strength of the springs provided, the yoke 12 will move away from the crosshead to the position represented by broken lines in Fig. 2.

My invention is most readily understood when considered with reference to an assumed operation thereof.

Assuming that an elevator counterweight, equipped with my automatic braking device, is traveling upward at high speed when the car is suddenly retarded, it will be apparent that the counterweight will continue to travel upward because of its momentum. This will cause slack in the cable above the counterweight, and, as soon as gravity has overcome the momentum of the ascending counterweight, it will begin to fall back.

However, as soon as the cable becomes slack, the yoke member 12 will be moved away from the cross-head to the broken line position shown in Fig. 2. Urged by the springs 8, the actuators 5 will move outwardas the rollers 9 move along. the diverging cam surfaces of the yoke 12. The wedges 7 will then be forced, by the springs 8, between the adjacent extremities of the rail gripping jaws 4:, thereby causing their outer extremities to grip the rails and prevent the falling back of the counterweight, with the resulting snapping of the cables.

This automatic operation will occur irrespective of whether the retardation of the elevator car is caused by the car striking the buffer, the setting of the car safety means, or in some other manner.

If the springs 8 are of insufiicient strength to hold the body when unsupported, they will still be effective to apply a snubbing force which will retard the falling back of the body. However, if the springs 8 are of sufiicient strength to prevent movement of the body, even though it is otherwise unsupported, the device will also serve as a safety means in the event of broken hoist cables.

When the elevator system is operating in the opposite direction (i. e., the car ascending and the counterweight descending) the sudden stoppage of the counterweight for any reason will cause the cable to become slack above the car. The device carried by the car will then go into operation to prevent the car falling back and snapping the cables, in a manner which is identical with the operation of the device on the counterweight, as set forth above.

In Fig. 4, a modified form of the invention is shown wherein the various elements of the device are similar to those shown in 1 but are disposed within the upper cross-head member. In this embodiment, the brackets 6 are secured to an upper plate 21 which is bolted to the upper side of the cross-head 15. The arrangement of the yoke 12 within the cross-head is such that it supports the car by engaging the lower side of the plate 21, as clearly shown in Figs. 4 and .6. The rail-gripping jaws are more compact, and each pair of jaws is pivoted upon a common pin.

It will be apparent that I have provided a braking device which is simple and positive in its action, and which may be provided upon elevator cars and counterweights to'preventthe falling back of either body, with the consequent snapping of the cables when the descent of the other body is suddenly retarded. The device is also effective to prevent the falling of the car or the counterweight in the event of ruptured cables. 7

Although I have shown and described certain specific embodiments of my invention, I am fully aware that many modifications thereof are possible. My invention therefore,

is not to be restricted except insofar as is necessitated by the prior art and by the spirit of the appended claims.

I claim as my invention:

1. A braking device for elevator cars or counterweights comprising brake shoes, means for biasing the brake shoes into engaging relation with the guide rails, restraining members associated with said brake shoes, movable cams normally held in engagement with the restraining members by the weight of the body on the hoist cable and movable to releasing position to disengage said restraining members when the tension on the hoist cables is released, whereby the brake shoes will be applied to retard the descent of the body.

2. A braking device for elevator carsor counterweights operating between guide rails comprising brake shoes, spring-pressed actuators to force the brake shoes into engagement with the guide rails, camsmovably mounted in engageable relation to said actuators and having surfaces of such conformation that, in one position, the actuators are maintained in an ineffective position and, in the second position, the actuators are released to apply the brake shoes to the guide rails, and means to move said cam surfaces to the second posiassociated jaws to grip the rails with sufficient force to mildly retard the car and prevent snapping the hoist cables, restraining means responsive to the normal tensioned condition of the hoist cables for holding the actuators in an inefi'ective position, and biasing means for moving said restraining means to'release the actuators when the tension of the hoist cables becomes less than a predetermined amount.

' In testimony whereof, I have hereunto subscribed my name this 12th day of June, 1930.

. JAMES DUNLOP.

tion whenever the hoist cable is slackened adjacent thereto.

3. A braking device for elevator cars or counterweights operating between guide rails comprising braking surfaces, springs for biasing said braking surfaces into engaging relation with the guide rails, means comprising cam surfaces effective to normally hold the springs compressed when the hoist cable is tensioned and to release the springs to permit the application of the brake when the tension of the hoist cable is released.

4. A braking device for elevator cars com.- prising, a pair of rail gripping aws on each side of the car adjacent the guide rails, an actuator member for moving each pair of jaws to rail gripping position, biasing means urging each actuator member to apply the 

